This invention relates to a seat recliner mechanism and more particularly to one adapted for motor vehicle applications in which the seat back can be reclined to various positions and also folded forward to permit access to the rear compartment area of the vehicle.
Many motor vehicle seats are now provided with recliner mechanisms which allow the position of the seat back with respect to the seat bottom to be adjusted as a means of enchancing occupant comfort and convenience. In installations where access to a rear compartment area of the vehicle requires the front seat back to be tilted forward, for example in typical two-door style passenger cars, the seat back reclining mechanism must also provide lost motion for such forward folding.
In one type of seat recliner mechanism presently in widespread use, a lower recliner structure supports the seat bottom and an upper recliner structure supports the seat back. A rotatable recliner gear is carried by one of the recliner portions (typically the lower), and a quadrant is provided having an arcuate toothed surface which meshes with the gear. The quadrant interacts with the other recliner structure to establish the reclined angle. By fixing or allowing rotation of the recliner gear, the reclined position of the seat can be adjusted or fixed as desired. As a means of increasing the ease of establishing a desired reclined position, a spring is provided which exerts a torsional force on the recliner gear or directly on the quadrant. This spring causes the seat back to be urged toward the driver, enabling the reclined position to be adjusted by releasing the recliner mechanism and varying the force that the occupant exerts against the seat back.
The recliner quadrant further includes features which provide for a predetermined range of lost motion between the quadrant and one of the recliner structures (typically the upper). This lost motion provides forward folding capability to permit access to the rear compartment area of the vehicle without releasing the recliner or changing the reclined position setting.
For recliner mechanisms of the type described above, there is a particular mode of operation which imposes extreme and potentially damaging stresses on the recliner components. If the seat back is folded forward while the recliner is set at a rearwardly reclined position and the recliner is then released, the recliner spring will cause the quadrant to be rotated in a no-load condition. Once the quadrant reaches the end of its travel, enormous shock loads are placed on the mechanism since the quadrant and recliner gear are accelerated to a high angular velocity and arrested almost instantly. Although the above operational scenario is quite unusual in actual field use since operators seldom actuate the recliner release unless they are sitting in the seat, seat mechanism designers must nonetheless accommodate this condition.
In accordance with the present invention, a recliner mechanism is provided which has features for preventing unrestrained rotation of the quadrant when the seat back is in a folded forward position. The mechanism includes a restraint pawl with a lever attached to it which detects the position of the upper recliner structure, and when the seat is folded forward, the pawl is allowed to fall into engagement with a stationary toothed arresting rack. When the pawl engages the rack, movement of the quadrant is restrained. However, when the seat back is folded rearwardly to its normal position, the pawl is moved out of engagement with the rack, thus permitting normal recliner operation.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims taken in conjunction with the accompanying drawings.